The present invention relates to azeotrope-like compositions of pentaflluoropropane, chloropropane, and dichloroethylene, to methods of using such compositions, to blowing agents containing the compositions, and to blown foams formed using such compositions. More particularly, the present invention relates to azeotrope-like compositions of 1,1,1,3,3-pentafluoropropane, 2-chloropropane and dichloroethylene.
Fluorocarbon based fluids have found widespread use in industry in a number of applications, including, as refrigerants, aerosol propellants, blowing agents, heat transfer media, and gaseous dielectrics. Because of the suspected environmental problems associated with the use of some of these fluids, especially chlorofluorocarbons (xe2x80x9cCFCsxe2x80x9d), it is desirable to use fluids of lesser ozone depletion potential such as hydrofluorocarbons, (xe2x80x9cHFCsxe2x80x9d) and/or hydrochlorofluorocarbons (xe2x80x9cHCFCs).
Thus, the use of fluids that do not contain CFCs or contain HCFCs or HFCs instead of CFCs, is desirable. Additionally, it is known that the use of single component fluids or azeotropic mixtures, which mixtures do not fractionate on boiling and evaporation, is preferred in many application, including as blowing agents for the production of rigid foams. Known methods for producing rigid foams generally comprise reacting an organic polyisocyanurate and a polyol in the presence of a blowing agent to form a rigid foam. See, for example, Saunders and Frisch, Volumes I and II Polyurethanes Chemistry and Technology (1962), which is incorporated herein by reference.
However, the identification of new, environmentally safe, azeotropic mixtures, particularly those well suited for use as blowing agents, is complicated due to the fact that azeotrope formation is not readily predicatble.
The present inventors have developed several compositions that can help to satisfy the continuing need for substitutes for CFCs and HCFCs. In one embodiment, the present invention provides azeotrope-like compositions comprising 1,1,1,3,3-pentafluoropropane (xe2x80x9cHFC-245faxe2x80x9d), 2-chloropropane, and dichlorethylene.
The preferred compositions of the invention provide environmentally desirable replacements for currently used CFC""s and HCFC""s. Additionally, the compositions of the invention exhibit characteristics that make the compositions better CFC and HCFC substitutes than any of 1,1,1,3,3-pentafluoropropane, 2-chloropropane and dichlorethylene alone.
One aspect of the invention provides a method for producing foams, preferably foams with relatively low k-factors. Applicants have discovered that methods for producing foams advantageously include providing to a foamable reaction mixture the azeotropic composition of the present invention as a blowing agent for the foamable mixture. Such methods, in preferred embodiments, produce rigid foams having desirably low k-factors. As used herein, the term xe2x80x9cfoamablexe2x80x9d reaction mixture refers to one or more compounds which, in the presence of a blowing agent, are capable of reacting to form a rigid foam. Another aspect of the present invention is a closed-cell foam produced according to the methods of the present invention.
The present compositions are azeotrope-like compositions. As used herein, the term xe2x80x9cazeotrope-likexe2x80x9d is intended in its broad sense to include both compositions that are strictly azeotropic and compositions that behave like azeotropic mixtures. From fundamental principles, the thermodynamic state of a fluid is defined by pressure, temperature, liquid composition, and vapor composition. An azeotropic mixture is a system of two or more components in which the liquid composition and vapor composition are equal at the state pressure and temperature. In practice, this means that the components of an azeotropic mixture are constant boiling and cannot be separated during a phase change.
As the term is used herein, xe2x80x9cazeotrope-likexe2x80x9d compositions behave like azeotropic mixtures, that is, they are constant boiling or essentially constant boiling. In other words, for azeotrope-like compositions, the composition of the vapor formed during boiling or evaporation is identical, or substantially identical, to the original liquid composition. Thus, with boiling or evaporation, the liquid composition changes, if at all, only to a minimal or negligible extent. This is to be contrasted with non-azeotrope-like compositions in which, during boiling or evaporation, the liquid composition changes to a substantial degree. All azeotrope-like compositions of the invention within the indicated ranges as well as certain compositions outside these ranges are azeotrope-like.
The azeotrope-like compositions of the invention may include additional components that do not form new azeotropic or azeotrope-like systems, or additional components that are not in the first distillation cut. The first distillation cut is the first cut taken after the distillation column displays steady state operation under total reflux conditions. One way to determine whether the addition of a component forms a new azeotropic or azeotrope-like system so as to be outside of this invention is to distill a sample of the composition with the component under conditions that would be expected to separate a non-azeotropic mixture into its separate components. If the mixture containing the additional component is non-azeotropic or non-azeotrope-like, the additional component will fractionate from the azeotropic or azeotrope-like components. If the mixture is azeotrope-like, some finite amount of a first distillation cut will be obtained that contains all of the mixture components that is constant boiling or behaves as a single substance.
It follows from this that another characteristic of azeotrope-like compositions is that there is a range of compositions containing the same components in varying proportions that are azeotrope-like or constant boiling. All such compositions are intended to be covered by the terms xe2x80x9cazeotrope-likexe2x80x9d and xe2x80x9cconstant boilingxe2x80x9d. As an example, it is well known that at differing pressures, the composition of a given azeotrope will vary at least slightly, as does the boiling point of the composition. Thus, an azeotrope of A and B represents a unique type of relationship, but with a variable composition depending on temperature and/or pressure. It follows that, for azeotrope-like compositions, there is a range of compositions containing the same components in varying proportions that arc azeotrope-like. All such compositions are intended to be covered by the term azeotrope-like as used herein.
The present invention provides azeotrope and azeotrope-like compositions comprising 1,1,1,3,3-pentafluoropropane, 2-chloropropane and dichloroethylene. Preferably, the novel azeotrope-like compositions of the present invention comprise effective amounts of 1,1,1,3,3-pentafluoropropane, 2-chloropropane, and dichloroethylene, preferably 1,2-dichloroethylene, and even more preferably trans-1,2-dichloroethylene. The term xe2x80x9ceffective amountsxe2x80x9d as used herein refers to the amount of each component which upon combination with the other component or components, results in the formation of the present azeotrope-like compositions.
These embodiments preferably provide azeotrope-like compositions comprising, and preferably consisting essentially of, from about 10 to about 99 parts by weight HFC-245fa, from about 1 to about 90 parts by weight of 2-chloropropane, and from about 1 to about 40 parts by weight of dichloroethylene. More preferably the azeotrope-like compositions of the present invention comprise, and preferably consist essentially of, from about 50 to about 99 parts by weight HFC-245fa, from about 1 to about 20 parts by weight of 2-chloropropane, and from about 1 to about 20 parts by weight of dichloroethylene. And even more preferably the azeotrope-like compositions of the present invention comprise, and preferably consist essentially of, from about 85 to about 99 parts by weight HFC-245fa, from about 1 to about 20 parts by weight of 2-chloropropane, and from about 1 to about 20 parts by weight of dichloroethylene.